Condenser



J. L. FINCH Jan. 19, 1937.

CONDENSER Filed July 20, 1935 INVENTOR JAMES L. HNCH ATTO R N EYPatented Jan. 19, 1937 PATENT OFFICE CONDENSER James L. Finch,Patchogue, N. Y., minor to Radio Corporation of America, a corporationof Delaware Application July 20, ms, sci-In N... 32,31:

llclaima.

This invention relates to an improved condenser and is particularlyadapted to condensers known as the antenna sleet-melting type, providedwith a suitable device for protecting the condenser against lightning.

An object of this invention is to simplify and improve sleet-meltingcondensers and to insure protection against the formation of a: steepwave-front voltage, such as is caused by lightning, during thunderstorms.

Another object of this invention isto provide a condenser which will beof greater utility without the need of constant attention.

Still another object of this invention is to provide a rugged, compactantenna sleet-melting condenser which has a self-contained inductanceconnected in series with the condenser and an external fuse and sparkgap, all of which provide adequate protection against the formation ofsteep wave-front voltage surges caused by lightning.

In condensers used in connection with antenna structures which aresubject to being loaded down with ice during periods of sleet formation,it has been found advisable to make arrangements for heating the wiresto remove such ice formation. In this connection it has frequently beenthe practice to employ condensers which pass radio-frequency currents,but which will serve to isolate the currents used for heating the wires,thus making possible the segregation of antenna conductors into circuitsthrough which heating current can be passed for melting oiiaccumulations, or to prevent the formation of sleet. These condensersare normally called sleet-melting condensers. In the past there havebeen many failures of these sleet-melting condensers due to excessivevoltages induced by lightning discharged in the vicinity of the antenna.

Therefore, as mentioned above, it is an object of this invention toprovide a condenser with means for protecting these condensers fromexcessive voltages.

In the prior art it has been customary to remove sleet-meltingcondensers at such periods of the year when lightning discharges arelikely to occur. This naturally involves considerable be necessary toremove the sleet-melting conexpense and by this invention it will nolonger' tected and a spark gap and fuse connected in shunt with thecondenser and inductance.

This invention will be more fully understood by referring to theaccompanying drawing, in which- Fig. 1 is a cross-section of an improvedcondenser, and

Fig. 2 is a side elevation of Fig. 1.

Referring now to the drawing, the condenser I, which is the ordinaryroll type non-inductive m condenser composed of alternate layers ofmetallic foil and insulating material wound upon a mandrel 2 which iscomposed of a central insulating member 3 and two terminal end members 4and 5. The condenser is placed 15 within an insulating casing or housing6 which has fastened at both ends a metallic end cap I which is rigidlysecured to housing 6 by means of suitable cement 8 flrmlykeyed togrooves 9 and I0. At one end of the casing a small in- 20 ductance coilII is connected to condenser I at a point I2 by means of a suitable nutI3 and washer I4. The upper end of the coil is secured to an insulatingdisc I5 which is retained by suitable nuts IB and II, the upper end ofthe 25 coil being connected by nuts I9 and 20 to a metallic washer 2|.It will be noted that the electrical circuit from the connection to theupper cap passes through the metallic washer and then through the wireinductance coil to 30 the upper terminal 4 of the condenser mandrel, thelower terminal mandrel 5 directly connecting the lower end of condenserI to the end cap 22. This end cap is provided with a lug 23 formechanically securing the condenser to the an- 35 tenna. The upper endof end cap I is threaded to receive a mechanical securing member 24which is provided with a mounted lug 25 similar to lug 23 in the end ofmember 22. A boss 26 is arranged on member 24 for securing a lug 2'! 40which is provided with suitable bolts 28 and nuts 25 and washers 30 fora fuse 3|, this fuse being a 50-ampere bare wire. However, this could beany other type, such as is used on general power lines.

on end cap 22 a boss 32, similar to boss 26, is arranged for securelymounting an insulating block 33 which is retained in place by a metallicstrip 34 by means of a bolt 35 and washers 36 and 31. The member 34 istapered at the 50 end to form one end of a spark gap at point 38. Theupper end of the insulating block 33 is provided with a metallic strip39 which terminates in a hollow semi-spherical member 40 which servesthe dual purpose of a rain shield and the other member of the spark gap.The bosses ll and I! are also provided with a terminal screw 4i and nut42. The spark gap is-set with such a spacing that it can be generallyrelied upon to remain open except in cases of excessive voltage. Inorder to make this gap reliable, it is necessary to use a fairly largespacing. The voltage necessary to break down such a gap is sometimes inexcess of the voltage for which it is practical to build sleet-meltingcondensers. cordingly, a simple spark gap connected in parallel with anordinary sleet-melting condenser does not afford suilicient protection.Therefore, by the placing of the inductance il in series with condenserI, the steep wave-front of the lightning voltage builds up asuiliciently high voltage across inductance coil ii to break down thespark gap' before the condenser has been charged to a sufficiently highvoltage which would damage the entire condenser structure.

The fuse II has such a current-carrying capacity that it will not bemelted for the average current induced by lightning discharges. However.in case the spark gap should become shortcircuited due to having beenaccidentally deformed, or due to the presence of foreign conductivematerials, then the fuse would melt it, upon application of heatingcurrent for melting off accumulations of ice, this heating currentshould pass through the fuse instead of through the portion of theantenna wire system intended. Otherwise the introduction of this sparkgap might prevent ice from being melted from certain portions.

Although only one modification of this invention has been shown, it willbe apparent that this invention may be applied to other types ofsleet-melting condensers in a similar manner. It will also be apparentthat different types of Q sleet-melting condensers will require slightlydifferent arrangements of the requisite parts, namely, theself-contained inductance coil, fuse and spark gap, for example, ametallic casing with one or more insulated terminal connections,supplied with series inductance and shunting spark gap and fuse.

'Iherefore, this invention should not be limited to the modificationshown, except such limitations as are clearly imposed by the appended Iclaim:

1. A sleet-melting roll condenser comprising an insulating casing,metallic end members having securing means for supporting saidcondenser, an inductance located at one end of said casing andelectrically connected in series with said condenser.

2. A sleet-melting roll condenser comprising an insulating casing,metallic end members having securing means for supporting saidcondenser, a metallic mandrel subdivided in the central portion of saidcondenser by an insulated member, an inductance electrically connectedin series with said condenser between said metallic end members.

3. A sleet-melting roll condenser comprising a casing, end membershaving securing means for supporting said condenser, an inductancelocated at one end of said condenser and electrically connected inseries between said metallic end members, and an external spark gap inshunt with said condenser and inductance.

4. A sleet-melting roll condenser comprising an insulating casing,metallic end m mbers hav- I ing securing means for supporting saidcondenser, a metallic mandrel sub-divided substantially in the centralportion thereof by an insulated member located at one end of said casingand an inductance electrically connected in series with said condenserbetween said metallic end members, and an external spark gap in shuntwith said condenser and inductance.

5. A sleet-melting roll condenser comprising an insulating casing,metallic end members having securing means for supporting saidcondenser, a metallic mandrel sub-divided substantially in the centralportion thereof by an insulated member, terminal means at one end ofsaid mandrel for connecting said condenser, and an inductanceelectrically connected in series with said condenser and between saidmetallic end members, and an external spark gap in shunt with saidcondenser and inductance.

6. A sleet-melting roll condenser comprising an insulating casing,metallic end members having securing means for supporting saidcondenser, an inductance electrically connected in series between saidmetallic end members, a fuse located on the outside of one end memberand a spark gap located on the outside of the other end member, saidspark gap and said fuse connected in series with each other and in shuntwith said condenser and said inductance.

'7. A sleet-melting roll condenser comprising an insulating casing,metallic end members having securing means for supporting saidcondenser, an inductance electrically connected in series between saidmetallic end members and said condenser, an external fuse and spark gapin shunt with said condenser and inductance.

8. A sleet-melting roll condenser comprising an insulating casing,metallic end members having securing means for supporting saidcondenser, an inductance electrically connected in series between saidmetallic end members and said condenser, a protective external spark gapand a single fuse wire connected in series with each other and in shuntwith said condenser and inductance.

9. A sleet-melting roll condenser comprising an insulating casing,metallic end members having securing means for supporting saidcondenser, an inductance electrically connected in series between saidmetallic end members and said condenser, an external spark gap having ahollow semi-spherical shield connected in shunt with said condenser andinductance.

10. An electrical condenser comprising an insulating casing, saidcondenser and an inductance both located within said casing, metallicend members secured to said casing, means for protection against steepwave-front voltages, said means comprising said inductance an externalfuse wire and a spark gap connected in series with each other andconnected in shunt with said condenser and said inductance.

11. An electrical condenser comprising an insulating casing, saidcondenser and an inductance both. located within said casing, metallicend members secured to said casing, said metallic end members havingapertures at each end for mechanically securing the condenser toexternal mounting means, means for protection against steep wave-frontvoltages, said means comprising said inductance an external fuse wireand spark gap connected in series with each other and in shunt with saidcondenser and said inductance.

JAMESLFINCH.

